Known power systems generally include damping members that act when the piston reaches an end-of-stroke region, both at the end of raising the undercarriage and at the end of lowering it. The actuators also include end-of-stroke dampers having pressure-control valves.
Nevertheless, under certain situations, the rod of the actuator can be subjected to high stresses. This applies, for example, at the end of a raising operation where the inertia of the undercarriage, together with the increase of pressure obtained in the end-of-stroke damping chamber and the driving force in the annular chamber generate high compression forces on the actuator rod. These forces are taken into account when dimensioning the actuator. Furthermore, when the undercarriage is lowered, it is desired to implement a sequence comprising, in succession: pressurizing the annular chamber, releasing the mechanical latch, and pressurizing the full section chamber, while simultaneously avoiding pressure peaks in the annular chamber.
The problem of the invention sets out to solve is that of designing a power system capable of avoiding the actuator rod being subjected to dangerous stresses, in particular at the end of raising the undercarriage.
Another object of the invention is to provide a power system whose structure is both simple and extremely reliable, and which can easily be added to existing installations.
Another object of the invention is to design a power system enabling pressure peaks to be avoided in the annular chamber of the actuator when lowering the undercarriage, and consequently making it possible to obtain a saving on the dimensioning of the actuator cylinder, and which also allows the undercarriage to be lowered in an emergency in the event of the hydraulic generator failing.